Free attended Canarsie High School in Brooklyn, New York before attending Guilford College in Greensboro, North Carolina. As a freshman he led Guilford's basketball team and helped the team win the NAIA National Championship and was named MVP of the NAIA Tournament.

He played for the San Diego Clippers, Philadelphia 76ers, Golden State Warriors, Cleveland Cavaliers and Houston Rockets in the National Basketball Association. He got his name from his days in Brooklyn, where a friend nicknamed him "World" because of his 44-inch vertical leaps and 360-degree dunks. He was known for taking high-risk shots and playing flamboyantly.

For both the 1978–79 and 1979–80 campaigns, George Gervin and Free were number 1 and 2 in the league in scoring. Free averaged 20.3 points per game over 13 seasons in the NBA. His best season was 1979–80 with the Clippers, averaging 30.2 points per game, as well as 4.2 assists per game and 3.5 rebounds per game in 68 games. He was an All-Star that season as well, although the Clippers failed to make the playoffs.

Free also played in the United States Basketball League (USBL) for the Miami Tropics after being waived by the Philadelphia 76ers on March 1987. He was USBL Man of The Year in 1987 and the Miami Tropics won the championship. His USBL stint took place the summer before Free went to the Houston Rockets for the 1987–88 season, which was his last NBA season. For Free, the highlight of that season was November 12, 1987, when he scored 38 points against the Sacramento Kings at Arco Arena and brought the Rockets back to win the game.